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Acetylenic Quinoxalinoporphyrazines as Photosensitisers for Photodynamic Therapy
Author(s) -
Mitzel Frieder,
FitzGerald Simon,
Beeby Andrew,
Faust Rüdiger
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200390140
Subject(s) - singlet oxygen , chromophore , chemistry , photochemistry , quantum yield , photodynamic therapy , solvent , molar absorptivity , absorption (acoustics) , singlet state , oxygen , fluorescence , organic chemistry , materials science , excited state , physics , quantum mechanics , nuclear physics , optics , composite material
A range of lipo‐ and hydrophilic derivatives of the new class of octaalkynyl tetra‐[6,7]‐quinoxalinoporphyrazines (TQuiPors), analogues of the naphthalocyanines, were prepared in two steps starting from functionalised hexa‐1,5‐diyne‐3,4‐diones. Divalent zinc and magnesium ions were introduced into the macrocyclic core. Whereas the triisopropylsilyl‐, 3,5‐di‐ tert ‐butylphenyl‐ and 4‐triisopropylsilyloxyphenyl‐terminated acetylenic TQuiPors are lipophilic and hence soluble in standard organic solvents, a polyethylene glycol‐substituted derivative was found to dissolve in DMSO as well as in ethanol/water mixtures. The new chromophores are characterised by intense UV/Vis/NIR absorptions, most notably by bands at 770 nm with extinction coefficients exceeding 500 000 M −1 cm −1 . With a view to possible photodynamic therapy applications, the potency of the chromophores to sensitise the formation of singlet oxygen was examined, both qualitatively using a 1,3‐diphenylisobenzofuran assay, and quantitatively by the determination of the singlet oxygen quantum yields. It was found that all TQuiPors produce singlet oxygen when irradiated in the presence of air. In particular, the octaalkynyl Zn‐TQuiPor generates singlet oxygen with a quantum yield of 56 %, thereby rivalling, and, in conjunction with its absorption profile, even exceeding the standards set by established PDT agents. The photostabilities of the TQuiPors were assessed and generally found to be satisfactory, but dependent on the solvent and the wavelength of the incident light.